In conventional xerographic systems, a performance maintenance system continuously checks the image generating process to ensure that the image quality is kept at predetermined standards. To accomplish this purpose, image patches are inserted on the photoreceptor belt in zones between the document zones generated by the user. The image patches are monitored and analyzed to adjust the process parameters. The monitoring, analyzing and adjusting process is performed whenever an image patch is present on the belt. With the newer multicolored systems there has been an increased burden on the performance maintenance system to schedule patches frequently in order to ensure acceptable image quality.
The scheduling process is computer driven and, according to the systems of the prior art, uses a fixed schedule of patch generation. This results in the maintenance process occurring at times where there is no need. Since patch generation requires the use of toner, an excessive amount of toner may be used in the image quality maintenance process. It is a purpose of this invention to provide an image quality maintenance system which schedules the generation of patches in an as needed basis to reduce the number of overall patches required.